Extinct Galapagos tortoise may be resurrected with genetics

Researchers find that a species of extinct galapagos tortoise has actually …

The Galapágos Islands played a key role in Darwin's formation of the theory of evolution. The different islands contain a variety of habitats and are remote enough that animals rarely colonized them. As a result, most of the species present are the descendants of these rare events, following diversification and adaptation. Preserving and studying this biological legacy has been recognized as valuable, both for its scientific and historical significance. That background should explain why researchers searched museums around the world for dead tortoises.

Not just any tortoise—a specific species of the famous Galapágos tortoises, which are exceptionally large and long-lived. Most islands in the chain had their own, distinct species of tortoise evolve (the largest island has four), but excessive hunting drove four of those species to extinction, including the one from the island of Floreana. An international team of researchers who were attempting to sort out the relationships among the different species obtained DNA from museum samples of the extinct Floreana variety.

What they found was a bit of a surprise. The DNA evidence indicated that Floreana had evolved a single species of tortoise, but that species' sequences also showed up in a few tortoises on the northern tip of the largest island. This population of animals had been a bit of an enigma; both on the DNA level and physically, they appeared to be hybrids, but researchers couldn't understand what they had hybridized with. The authors suggest that a ship that was hunting tortoises on the island had dropped a few Floreana natives off when gathering more, allowing the species to establish a genetic foothold on the far end of a different island.

The researchers identified sixteen tortoises that appeared to contain various amounts of Floreanan DNA. Because the animals are so long-lived, most were only two generations into the hybridization process, having mated with either natives or other hybrids. The authors raise the possibility that careful matings based on DNA analysis could largely recreate the genome of the extinct Floreana tortoise.

That doesn't mean doing so is necessarily a good idea; the Galapágos Islands face an array of environmental threats, and it's not clear that diverting resources to a DNA-based breeding program is their best use. The fact that the tortoises can successfully hybridize with those from neighboring islands raises questions about whether these animals represent a truly distinct, one-of-a-kind species, or if even the best breeding program can resuscitate a fully Floreanan genotype. Of course, given how slowly these animals mature, it's entirely possible that the project would take very little in the way of resources in any given year.